Self-locking suture anchor

ABSTRACT

A tissue anchor having a length of filament held so that an applied force greater than a threshold force will cause the filament to move longitudinally, while an applied force less than the threshold force will not move the filament, and methods of attaching soft tissue to bone using such an anchor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.11/052,557 filed on Feb. 7, 2005 and entitled “Self-Locking SutureAnchor,” which is a continuation of U.S. patent application Ser. No.10/629,978 (now U.S. Pat. No. 7,081,126), filed on Jul. 30, 2003 andentitled “Self-Locking Suture Anchor,” which is a continuation of U.S.patent application Ser. No. 10/375,389 (now U.S. Pat. No. 6,660,023),filed on Feb. 27, 2003 and entitled “Self-Locking Suture Anchor,” whichis a continuation of U.S. patent application Ser. No. 09/371,411 (nowU.S. Pat. No. 6,527,794), filed on Aug. 10, 1999 and entitled“Self-Locking Suture Anchor.” These references are hereby incorporatedby reference in their entireties.

BACKGROUND OF THE INVENTION

This invention relates to surgical fasteners, e.g., anchors that securesutures to bone, a meniscus, or other tissue. It further relates to asuture anchor that attaches a suture to tissue without the use of knots,and to methods of securing tissue using one or more anchors and a lengthof suture.

Many surgical procedures require the attachment of soft tissue, e.g.,ligament or tendon grafts, to bone. This is typically accomplished byanchoring a suture in bone, for example with a screw, pin, or other boneanchoring device, and looping the suture around or stitching the sutureto the soft tissue. When this process is completed, the surgeongenerally must knot the suture to secure the tissue. This knottingprocess can be difficult and tedious, particularly during laparoscopicor endoscopic procedures, where the surgeon must remotely manipulate thesuture using tools inserted through an endoscopic tube. Further, as manyas six knots are often required to secure one suture. These knots may“stand proud” above the tissue and interfere with movement and healing.

One advance which has been proposed is the anchor apparatus disclosed byGoble, et al., in U.S. Pat. No. 5,702,397. That apparatus comprises ananchor body through which a suture passes, and which contains a clampingmechanism such as a spherical element within the anchor body. When thesuture is pulled in a proximal direction, the clamp is urged intocontact with the anchor body, thereby holding the suture in place. Whenthe suture is pulled in a distal direction, the clamp disengages, andthe suture can move freely through the anchor body. At least one end ofthe suture is stitched and/or knotted to soft tissue.

Several knotless suture anchor assemblies have recently been proposed byThal in U.S. Pat. Nos. 5,569,306; 5,658,313; 5,665,112; and 5,683,419.These describe suture anchors which secure a filament having a smallloop at one end. In some embodiments, another length of suture ends in asmall block, which is passed through the loop to secure the tissue.While these structures can be secured without knots, the block used tosecure the suture may itself stand proud above the tissue, causingdiscomfort and interfering with healing. In other embodiments, theanchor itself is passed through the small loop, creating a larger loopwhich is used to hold tissue.

U.S. Pat. No. 5,709,708, also by Thal, describes a suture anchorutilizing a continuous loop of suture material, which secures the tissuein a similar manner. As in the other Thal knotless anchors, the tensionof the suture is dependent on the length of specially provided suture,which cannot be adjusted. Thus, these anchors cannot be used in surgicaloperations in which it is necessary to tighten a loop of suture tosecure soft tissue.

The tying of suture knots presents difficulties in other surgicalprocedures, as well. For example, tears occur commonly in the menisci ofathletes. The simplest method of repairing such a tear is to stitch itclosed by passing a length of suture through the tissue and tying.However, the needles used in such surgery are very difficult tomanipulate during endoscopic surgery, and the knots used to secure thesuture may interfere with healing as described above. These difficultiesare particularly severe in the restricted space of the joint capsule ofthe knee, a common location for such injuries. Other devices such asdarts and clamps have also been proposed for this purpose; see forexample U.S. Pat. Nos. 5,154,189; 5,269,783; and 5,702,462. Like sutureknots, these devices may cause considerable discomfort during healing ofthe tear. Further, if made of non-bioabsorbable materials, a secondsurgery must be performed to remove the devices from the meniscus afterhealing.

A need thus exists for an improved technique and apparatus for securingtissues without the use of knots. A further need exists for suchtechniques and apparatus which also permit the position of the suture tobe readily adjusted. A still further need exists for such apparatuswhich is small enough to avoid discomfort, which is amenable tofabrication from bioabsorbable materials, and which can be used eitherin bone or in soft tissue.

SUMMARY OF THE INVENTION

The above needs are among those met by the invention, which provides ananchoring device that can be embedded in bone or soft tissue, thatpermits suture length and/or tension to be readily adjusted, and thatcan be secured without the use of knots.

In one aspect of the invention, a suture anchor suitable to be embeddedin bone has a cavity which holds a filament (e.g., a suture) byinterference fit. The anchor holds the suture tightly enough to resist“operational” forces to which the suture is subjected subsequent todeployment, e.g., during movement of the bones and/or soft tissues towhich the suture is attached. However, the interference fit is weakenough to allow the suture to be pulled longitudinally through thecavity by a stronger force.

In use, such an anchor can be placed with some slack in the suture. Thesuture can then be tightened by pulling on one of its ends (with thelarger force). It is an advantage of the invention that the tighteningof the suture can be reversed, simply by pulling on a loop formed by thesuture or by pulling on its opposite end. The suture does not loosen innormal use, however, since the forces required to move during deploymentare greater than those exerted by the bones and/or tissues to which itis attached.

In a related aspect, the anchor may hold the suture at two points,forming a loop. The loop can be disposed around tissue and, then,tightened by pulling one end of the suture, thereby securing the tissue.Again, if the loop is drawn too tight, it can be loosened by pullingfirmly.

The invention also provides methods for attaching soft tissue to bone.In these methods, an anchor of the type described above can be emplacedin bone. The soft tissue is secured by stitching or by catching aportion of the tissue in a loop of suture, which is subsequentlytightened. The suture can be tightened or loosened as necessary duringdeployment, and need not be knotted.

These and other aspects of the invention are evident in the drawings andin the description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is best understood with reference to the drawings, inwhich:

FIGS. 1 and 2 are illustrations of suture anchors according to theinvention, adapted to be embedded in bone;

FIG. 3 is an illustration of a suture anchor according to the inventionbefore deployment; and

FIGS. 4A-4C illustrate a deployment process for the anchors shown inFIGS. 1 and 2.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 a shows a cutaway view of a suture anchor according to theinvention. The anchor comprises an anchoring element 10, which isadapted to be embedded in a bone tunnel or in soft tissue, and comprisesan axial channel 12. In the embodiment shown, element 10 comprises aseries of ridges 14 on its outer surface, which aid in securing theelement, for example, in a bone tunnel. It will be understood that theridges 14 are not a necessary element of the anchor, and may be omittedif desired. The anchor 10 further comprises an insertion stem 16. Whenthe anchor is in the deployed position shown in FIG. 1 a, the insertionstem 16 is held within the axial channel 12, e.g., by interference fit.In preferred embodiments, the insertion stem 16 is slightly larger thanthe axial channel 12, so that the stem 16 forces the anchoring element10 to expand when it is inserted therein, thereby securing the anchorfirmly in the bone tunnel.

The anchor further comprises a filament 18, e.g., a suture, disposedbetween the anchoring element 10 and the insertion stem 16. In thepreferred embodiment shown in FIGS. 1 a and 1 b, the insertion elementcomprises a suture channel 20. This channel guides the suture 18, andholds it in compression against the anchoring element 10. Theconfiguration of anchoring element 10, insertion stem 16, and suture 18can be seen clearly in FIG. 1 b, which shows a cross-sectional view ofthe anchor at the point indicated by the arrows of FIG. 1 a. The mildcompression of the suture 18 in the channel 20 provides a frictionalresistance to prevent movement of the suture when tension is applied toone of its free ends 22. This frictional resistance is overcome when atension greater than the threshold tension is applied to a free end ofthe suture. The suture 18 may then slide longitudinally through thechannel 20, allowing the length of the free ends 22 to be adjusted.

It will be understood that the configuration of suture 18 in FIG. 1represents only one of many possible embodiments of the invention. Inparticular, it will often be preferable to pass the suture between theinsertion stem 16 and the anchoring element 10 multiple times, forexample, in order to form a loop segment. In other embodiments of theinvention, the compression of the suture may be stronger, so that thethreshold tension which would be necessary to move the suture is closeto or exceeds the breaking strength of the suture. In such embodiments,the length of the free ends is no longer adjustable once the compressionon the suture is applied.

In one such embodiment, the suture (or other filament) may be formedwith a small loop at one end, which is used to secure the suture to theanchor. This embodiment is illustrated in FIGS. 2 a and 2 b; the formerdepicting a cross-section of the anchor along the axis of symmetry; andthe latter depicting a transverse section. The head of suture 18comprises a small loop 28; e.g., disposed at the distal end of theanchor. The suture passes between the insertion stem 16 and theanchoring element 10, forms a loop segment 26, and passes back betweenthe insertion stem and the anchoring element. The suture then passesthrough head loop 28, back up between the insertion stem 16 and theanchoring element 10, and ends in free end 22. The loop segment 26 canbe tightened by pulling free end 22, and loosened by pulling the loopsegment 26 itself. Because of the mechanical advantage afforded bylooping of the suture, the force required to loosen the suture bypulling on loop 26 is twice the force required to tighten the suture bypulling on free end 22. In the embodiment shown, the suture passesthrough two channels 23, 25 in the anchor 16; one of these channels 25could be eliminated so that the suture would pass around the head of theanchor.

FIGS. 3 a and 3 b illustrate a different embodiment of the anchor, inwhich the suture is secured by a small knot 27 rather than a loop. FIG.3 a is a plan view of the anchor, and FIG. 3 b is a longitudinalcross-section.

FIGS. 4 a-4 c illustrate a deployment process for the anchors shown inFIGS. 1 and 2. Only a portion of the suture is shown in FIGS. 4 a-4 c;preferably, the suture will be looped in the fashion shown in FIG. 2 orFIG. 3. FIG. 4 a shows an anchor placed in bone tunnel 32, connected todeployment apparatus 34. FIG. 4 b illustrates the insertion element 16being pulled into the axial channel 12 of anchoring element 10. Tensionis applied to the stem of insertion element 16 (in the direction shownby arrow A) by the colleted stem-pulling portion of the deploymentdevice 34, while the anchoring element 10 is held substantially immobilewithin bone hole by the anchor-holding portion of that device. Theseforces act to move the insertion element 16 in the direction of arrow Asuch that larger diametered portion of insertion element is pulled intothe axial channel 12 of anchoring element 10. As a result, the wall ofthe anchoring element 10 expands outwardly and into the walls of thebone hole 32. As shown in FIG. 4 c, the insertion stem is pulledproximally through the axial bore 12, until further motion is retainedby abutment of flange 36 with the distal end of anchoring element 10. Atthis point, the deployment device continues to exert tension on the stem16, causing frangible portion 38 to shear. This facilitates removal ofthe excess portion of the stem 16 and, likewise, disengages thedeployment device 34. The suture 18 can be adjusted by pulling firmly onfree end 22.

The suture anchors of the invention can be provided in a variety ofsizes and materials, depending on the intended application. For example,a typical anchor intended to be embedded in the shoulder blade, for usein repair of the rotator cuff of an adult, might have a length in therange of 8-15 mm and a diameter in the range of 3-6 mm. Such an anchormight be capable, for example, of holding a #2 suture with a thresholdforce in the range of 25-35 lbs. (As it is used herein, the term“threshold force” describes a pulling force above which a filament moveslongitudinally through an anchor, and below which the filamentsubstantially does not move through the anchor). It is generallydesirable for the anchor to consist of biocompatible material, e.g.,implant grade high density polyethylene, low density polyethylene (PE6010 and PE 2030), polypropylene (13R9A and 23M2: all made by Rexene,Dallas, Tex.) or surgical implant grade steel. In some embodiments, theanchor may comprise a bioabsorbable material, e.g., poly-1-lactide or alactide-glycolide composition.

In an exemplary embodiment of the methods of the invention, the anchorillustrated in FIGS. 3 a and 3 b can be used to repair a torn rotatorcuff by reattachment of the rotator cuff to the scapula. An anchor suchas that illustrated in FIG. 3 a, which holds a loop of suture byinterference fit, is embedded in a tunnel drilled, for example, in thescapula. The loop of suture and the free end of the suture extend outfrom the scapula at the proximal end of the anchor.

When the anchor is disposed in the bone tunnel, a portion of the tornrotator cuff is passed through the suture loop. The loop is thentightened by pulling with a force greater than the threshold force onthe free end of the suture. This tightens the loop, drawing the tissueagainst the anchor and securing it to the bone without knotting thesuture. The free end of the suture may then be trimmed, if desired.

The invention may be used with various anchor designs, depending on thenature of the surgical repair. In particular, designs similar to thosedescribed in copending U.S. application Ser. No. 08/813,914, e.g., atFIG. 5 and in the accompanying text, and in copending U.S. applicationSer. No. 08/814,149, and in the accompanying text, both of which areincorporated herein by reference, may be adapted to hold a suture inaccordance with the teachings herein.

Other embodiments of the invention will be apparent to those skilled inthe art from a consideration of the specification or practice of theinvention disclosed herein. For example, while the invention has beendescribed primarily in the contexts of securing soft tissue to bone andof repairing tears in soft tissue, it may also be used to secure orrepair cartilage, ligaments, or other tissues. It is intended that thespecification and examples be considered as exemplary only, with thetrue scope and spirit of the invention being indicated by the followingclaims.

1. A method for anchoring a suture, comprising: implanting an anchormember in bone, the anchor member having a cavity extending therethroughwith opposite open ends; moving a deployment shaft to position insertionelement in the cavity in the anchor member, the insertion element andthe anchor member engaging a suture extending through the cavity to locka loop of suture extending from the cavity in a fixed position; andfrangibly detaching the deployment shaft from the insertion element. 2.The method of claim 1, wherein the suture is held between the anchormember and the insertion element by a compression fit.
 3. The method ofclaim 1, wherein moving the deployment shaft comprising pulling thedeployment shaft to pull the insertion element into the cavity.
 4. Themethod of claim 1, wherein frangibly detaching the deployment shaft fromthe insertion element comprises applying tension to a frangible portionformed between the deployment shaft and the insertion element.
 5. Amethod for anchoring tissue to bone, comprising: implanting an anchormember in a bone tunnel; applying tension to a deployment shaft attachedto an insertion element to pull the insertion element into a cavityformed in the anchor member; applying tension to a frangible portionformed between the deployment shaft and the insertion element to causethe frangible portion to shear to separate the deployment shaft from theinsertion element.
 6. The method of claim 5, wherein the insertionelement is held within the cavity of the anchor member by aninterference fit.
 7. The method of claim 5, wherein the anchor memberincludes a suture extending therethrough, and wherein the suture isengaged between the anchor member and the insertion element.
 8. Themethod of claim 7, wherein the suture extends through the cavity, formsa loop segment, and extends back through the cavity.
 9. A method foranchoring tissue to bone, comprising: implanting an anchor element in abone tunnel, the anchor element having a suture passing through a cavityin the anchor element, forming a loop segment, and passing back throughthe cavity in the anchor element; and inserting an insertion elementinto the cavity in the anchor element to hold the suture therein byinterference fit.
 10. The method of claim 9, wherein the insertionelement is inserted into the cavity in the anchor member using adeployment device.
 11. The method of claim 10, wherein the deploymentdevice is attached to the insertion element during deployment, andwherein the deployment device is frangibly sheared from the insertionelement after deployment of the insertion element into the anchormember.
 12. The method of claim 10, wherein the deployment device ispulled to pull the insertion element into the cavity in the anchormember.